Windows Phone开发手记－WinRT下自定义圆形ItemsControl

2022-07-11 12:57:43

这里的ItemsControl指的是Xaml里的集合控件，包括ListView，GridView等，此篇博客主要参考MSDN Blog的一篇文章，具体出处为：http://blogs.msdn.com/b/mim/archive/2013/04/16/winrt-create-a-custom-itemspanel-for-an-itemscontrol.aspx ，同时做了对Windows Phone的一些修改和适配。

首先，正常的GridView，和ListView的样式我就不在这里列出了，今天我们重点谈的就是如何实现一个圆形布局的ListView／Gridview。

自定义圆形ItemsControl

Windows Phone 8.1 Windows

这里我填充的Item只是简单的Image，但是并不妨碍其实现效果，这样的布局完全可以带来更惊艳的交互体验。

同时如原文所说这里提供的源码只是实现基本布局，并未提供更多的动画，手势，交互等功能，大家可以自行填充。

为了实现自定义的布局，我们需要自定义ItemsPanel来替换ItemsControl的模版，我们自定义的ItemsPanel必须继承于Panel类。

下面我们需要重写以下两个方法 :

MeasureOverride :使用MeasureOverride方法来报告你所需空间的数量
ArrangeOverride : 使用ArrangeOverride方法在你的ItemsPanel中真实的布局Item

//CircleItemsPanel.cs
using System;
using Windows.Foundation;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml;

namespace CustomItemsPanel
{
    public class CircleItemsPanel :Panel
    {
        public double Radius {
            get {
                return (Double)GetValue(RadiusProperty);
            }
            set {
                SetValue(RadiusProperty, value);
            } }
        public static readonly DependencyProperty RadiusProperty = DependencyProperty.Register(
            "Radius", typeof(Double),typeof(CircleItemsPanel),new PropertyMetadata(100d,RadiusCallBack));

        private static void RadiusCallBack(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var radialPanel = (CircleItemsPanel)d;
            radialPanel.InvalidateArrange();
        }

        protected override Size MeasureOverride(Size availableSize)
        {
            var s= base.MeasureOverride(availableSize);
            foreach (var element in this.Children)
            {
                element.Measure(availableSize);
            }
            return s;
        }
        protected override Size ArrangeOverride(Size finalSize)
        {
            this.Clip = new RectangleGeometry {Rect=new Rect (0,0,finalSize.Width,finalSize.Height) };
            var i = 0;
            var degreesOffset = 360.0 / this.Children.Count;
            foreach(var elemet in this.Children)
            {
                var centerX = elemet.DesiredSize.Width / 2.0;
                var centerY = elemet.DesiredSize.Height / 2.0;
                var degreesAngle = degreesOffset * i++;
                var transform = new RotateTransform { CenterX=centerX,CenterY=centerY,Angle=degreesAngle };
                elemet.RenderTransform = transform;
                var radianAngle = (Math.PI * degreesAngle) / 180.0;
                var x = this.Radius * Math.Cos(radianAngle);
                var y = this.Radius * Math.Sin(radianAngle);
                var rectX = x + finalSize.Width / 2 - centerX;
                var rectY = y + finalSize.Height / 2 - centerY;
                elemet.Arrange(new Rect(rectX,rectY,elemet.DesiredSize.Width,elemet.DesiredSize.Height));
            } 
            return finalSize;
        }
    }
}

至于里面数学知识的应用我就不细说，我大天朝的基础教育还是杠杠滴，贴张图大家就会明白的。

在Xaml中使用我们的圆形Panel，到此就大功告成啦。

<Page
    x:Class="CustomItemsPsnnel.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:CustomItemsPsnnel"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    
    DataContext="{Binding Path=Main, Source={StaticResource Locator}}"
    Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">

    <Grid>
        <TextBlock HorizontalAlignment="Center" Style="{StaticResource TitleTextBlockStyle}" Text="{Binding Title}"/>
        <GridView HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
            <GridView.ItemsPanel>
                <ItemsPanelTemplate>
                    <local:CircleItemsPanel Radius="100" Height="600" VerticalAlignment="Stretch"/>
                </ItemsPanelTemplate>
            </GridView.ItemsPanel>
            <GridView.Items>
                <Image Width="50" Source="iTunesArtwork.png"/>
                <Image Width="50" Source="iTunesArtwork.png"/>
                <Image Width="50" Source="iTunesArtwork.png"/>
                <Image Width="50" Source="iTunesArtwork.png"/>
                <Image Width="50" Source="iTunesArtwork.png"/>
                <Image Width="50" Source="iTunesArtwork.png"/>
                <Image Width="50" Source="iTunesArtwork.png"/>
                <Image Width="50" Source="iTunesArtwork.png"/>
                <Image Width="50" Source="iTunesArtwork.png"/>
            </GridView.Items>
        </GridView>
    </Grid>
</Page>

总结了一下，发现原来Xaml下的自定义控件可以这么简单，这么*，实在给我后续的开发打开了一扇新的大门，以前的自定义都只是限于定制Style，Template，相信以后回有更多好玩app会诞生，最后贴张图。

Windows Phone开发手记－WinRT下自定义圆形ItemsControl

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